31 July 2009

Overfishing: having your fish and eating it too

A landmark collaboration between ecologists and fisheries management experts suggest that global commercial fisheries could be rebuilt with careful management.

Among the key achievements is the fact that the study was done at all. Antagonism between ecologists and fisheries management experts has been intense, and the collaborators hope the study will inspire similar collaborations between scientists whose focus is safely exploiting specific natural resources and those interested mainly in conserving them.

The collaboration began in 2006 when Boris Worm, a marine ecologist at Dalhousie University in Halifax, Nova Scotia, and other scientists made an alarming prediction: if current trends continue, by 2048 overfishing will have destroyed most commercially important populations of saltwater fish. Ecologists applauded the work. But among fisheries management scientists, reactions ranged from skepticism to fury over what many called an alarmist report.

Key findings include:

"A number of systems were at least heading in the right direction". Out of 10 regions in North America, northern Europe and Oceania that his team looked at closely, five showed signs of improvement, with diminishing rates of exploitation in recent years. For the most part, fish populations in Alaska and New Zealand never plummeted drastically because of good management from the start. Fisheries in the Baltic Sea, North Sea and off the coast of the UK and Ireland, however, tend to face continued declines in stocks.

More discriminate fishing gear targeted to large individuals of specific species, government-imposed catch limits, and the creation of marine reserves all helped rebuild stocks. But there is not one solution. In order to avoid collapse you need to do a number of things, there is not one solution that will get you there."

The researchers also agreed that solutions did not lie only in management techniques but also in the political will to apply them, even if they initially caused economic disruption.

The researchers caution that much work remains to be done to end global overfishing, as a large fraction of global fisheries are not properly managed, reported or regulated. Particularly outside wealthy industrialized nations, prospects for reducing fishing mortality are often more limited unless fishers get access to alternative sources of food and income. Therefore a more global perspective on rebuilding marine resources is necessary.

Those involved in the study also found out why ecologists and management scientists disagreed so sharply in the first place. As long as a fish species was sustaining itself, management scientists were relatively untroubled if its abundance fell to only 40 or 50 percent of what it might otherwise be. Yet to ecologists such a stock would be characterized as “depleted”.

The researchers suggest that a calculation of how many fish in a given species can be caught in a given region without threatening the stock, called maximum sustainable yield, is less useful than a standard that takes into account the health of the wider marine environment.

Full media articles on the wildsingapore news blog.

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